Various apparatus are known which are suitable for mixing molding or impression materials such as are used in the dental field. The equipment used to mix the dry materials and liquid should permit such mixing to occur without bubble formation.
German DE-OS No. 27 13 152 discloses a mixing apparatus for dental molding materials having a mixing cup with openings into which the fingers of the mixing apparatus project. Additional fingers are arranged in the mixing cup cover and these are spaced with respect to the former fingers. The molding material is mixed by rotating the fingers of the mixing apparatus. However, poor and incomplete mixing is obtained because of the movement of the rotating fingers in the mixing zone resulting in a non-uniform molding material. German DE-OS No. 30 22 689 disclosed another mixer wherein the mixing cup is constructed as a dish with an annular channel having a V-shaped profile and into which a rotating counter-cone projects with a vertical rotating axis. Mixing takes place by rotating the dish and counter-cone. Driving takes place with the aid of envelope drives, both for the counter-cone and the dish. The apparatus has relatively complicated construction and due to the special shape of the dish, is large.